Presently, many agricultural and industrial vehicles are equipped with a cab structure which is mounted to the frame of the vehicle by isolating members, such as shock absorbers or rubber mounts. In such vehicles, the transmission is normally fixed secure to the frame while the controls for the transmission are positioned within the cab structure. This setup presents a problem in that the control linkage, which connects the shift lever to the transmission, experiences unwanted motion as the vehicle moves over uneven terrain. Such motion becomes detrimental to the operation of the vehicle when it is large enough to effect shifting of the transmission.
Up until now, flexible cables such as push-pull cables have been commonly used in such applications. These cables however, often experience lost motion, frictional drag, sharp bends and high loading, which in some instances can create large variations between gear speeds which cannot be tolerated. Rigid linkages on the other hand, are better able to handle lost motion in high loading situations but they have the distinct disadvantage in that they cannot compensate for variations in motion without shifting gears. U.S. Pat. No. 3,616,709 entitled "Transmission Control Mechanism For A Tractor Having A Resiliently-Mounted Control Console" is one patent which employs a rigid link system such that relative motion is minimized when the shift lever is in a given position. However, there is still a need in the industry to provide a control linkage which can tolerate the relative motion which is imparted between the cab strucutre and the transmission of a vehicle while preventing displacement of the gear shift mechanism.
Now a control linkage has been invented which satisfies this problem.